{"record":{"id":"410b08261f587f76","repo":"ComposioHQ/composio","slug":"failed-to-fetch-file-from-url-e-cause","errorCode":null,"errorMessage":"Failed to fetch file from URL: {e.cause}","messagePattern":"Failed to fetch file from URL: (.+?)","errorType":"validation","errorClass":"ValidationError","httpStatus":null,"severity":"error","filePath":"python/composio/core/models/tool_router_session_files.py","lineNumber":146,"sourceCode":"                response.close()\n                raise _UrlFetchError(\n                    size_detail=\"Response size exceeds maximum allowed size\"\n                )\n            chunks.append(chunk)\n    response.close()\n\n    mimetype = response.headers.get(\"content-type\", \"application/octet-stream\")\n    mimetype = mimetype.split(\";\")[0].strip()\n    return b\"\".join(chunks), mimetype\n\n\ndef _fetch_from_url(url: str) -> t.Tuple[bytes, str]:\n    \"\"\"Fetch file content from a user-supplied URL. Returns (content, mimetype).\"\"\"\n    try:\n        return _fetch_url_bytes(url)\n    except _UrlFetchError as e:\n        if e.cause is not None:\n            raise ValidationError(f\"Failed to fetch file from URL: {e.cause}\") from e\n        if e.redirected:\n            raise ValidationError(\n                \"URL returned redirect. Please provide a direct URL to the file.\"\n            ) from e\n        if e.status_code is not None:\n            raise ValidationError(\n                f\"Failed to fetch file from URL: {e.status_code} {e.status_text}\"\n            ) from e\n        raise ValidationError(str(e)) from e\n\n\nclass RemoteFile:\n    \"\"\"Represents a file stored in a tool router session's file mount.\n\n    Provides methods to fetch, save, and work with the file content.\n    \"\"\"\n\n    def __init__(","sourceCodeStart":128,"sourceCodeEnd":164,"githubUrl":"https://github.com/ComposioHQ/composio/blob/64b1b85502b1beeb2379e6c9e8bf1104504fa637/python/composio/core/models/tool_router_session_files.py#L128-L164","documentation":"Raised while uploading files by URL: _fetch_from_url tried to download the user-supplied URL and the underlying fetch failed with a network-level cause (DNS failure, TLS error, refused connection). The specific cause is embedded in the message and chained.","triggerScenarios":"Passing a url=... input to the session file upload API where the host is unreachable, DNS doesn't resolve, or a proxy blocks the egress request from the Composio backend.","commonSituations":"Internal/localhost URLs not reachable from the internet, corporate proxies, transient DNS failures, typos in the hostname.","solutions":["Verify the URL is publicly reachable (curl -I from an external host)","Use pre-signed public URLs (S3/GCS/Drive direct links)","If the file is local, upload bytes/path directly instead of by URL","Retry to rule out transient DNS/network issues"],"exampleFix":"# before\nfiles.add(url='http://localhost:8000/report.pdf')\n\n# after\nwith open('report.pdf','rb') as f:\n    files.add(content=f.read(), filename='report.pdf')","handlingStrategy":"validation","validationCode":"from urllib.parse import urlparse\nu = urlparse(url)\nassert u.scheme in ('http','https') and u.netloc, 'bad URL'","typeGuard":null,"tryCatchPattern":"try:\n    files.add(url=url)\nexcept ValidationError as e:\n    # fall back to direct upload\n    files.add(path=local_copy)","preventionTips":["Use publicly reachable URLs","Upload bytes directly for local files"],"tags":["python","files","upload","url-fetch","network"],"backgroundTag":"url-fetch-failed","analyzedSha":"64b1b85502b1beeb2379e6c9e8bf1104504fa637","analyzedAt":"2026-08-28T15:39:33.623Z","schemaVersion":2},"datasetVersion":"2026-08-28T16:17:29.566Z"}